1. Field of the Invention
The present invention relates to a communication signal receiver for estimating an imaginary-part component of a complex data signal and a related method, and more particularly, to an apparatus and a related method for adjusting tap coefficients of a feed-forward filter to improve an estimated result of the imaginary-part component at least according to phase error information.
2. Description of the Prior Art
In communication systems, inter-symbol interference (ISI) is a common phenomenon. The primary cause of ISI is multipath propagation. Hence, an equalizer is typically adopted in signal receivers for reducing the effect resulted from multipath propagation during signal transmission.
When processing a complex signal (such as a VSB signal) by using the equalizer, the optimum situation is to respectively process the real-part component and the imaginary-part component of the complex signal by adopting their own equalizers. However, the process is too complicated since the equalizer has too many parameters and tap numbers. A current common approach is to perform a Hilbert transform upon the real-part component of the complex signal to obtain the estimated value of the imaginary-part component, so as to replace the originally required equalizer of the imaginary-part component. Since the Hilbert transform used in the VSB signal is not an ideal Hilbert transform in a conventional signal processing, this approach seems not good enough when the phase error is slightly larger.